Proper care of brakes

Press, Volume CXI, Issue 32640, 23 June 1971, Page 10

Proper care of brakes

Brakes are one of the most important safety items on any car, new or old, but if as-new safety is to continue, the braking system must be properly maintained. The rule “if it works all right leave it alone,” does not apply to braking systems, the Lockheed company reports. And the ultimate responsibility lies with the car owner, who must make sure his brakes are correctly cared for. In spite of handbook recommendations, many owners do not realise that brake-fluid levels must be checked once a month or every 1000 miles whichever comes first, the company says. Here are some of the answers the company has given to many frequentlyasked questions about car braking systems— Why do some companies recommend that brake fluid be changed every 18 months or 24,000 miles? Because all brake fluids tend to be hydroscopic to some degree, and in order to avoid any possibility of contamination through exposure to the atmosphere fluid in the system should be changed at this interval. Can a power brake conversion kit be fitted to any make of car? Yes. The kite contain all the necessary components

for a conversion—except for some older vehicles which require additional fittings, and Continental vehicles which may require special metric parts. It is important that all components of the braking system are in first class condition before the servo is fitted. A servo is intended to take the physical effort out of braking—not necessarily to increase the performance. Why not use copper tubing for hydraulic brake systems rather than “bundy” tubing? Due to the higher burst strength of “bundy” tubing a greater safety margin is provided which is particularly necessary for the increased hydraulic pressures used in disc brake systems. What are the causes of excessive pedal travel? Most likely due to need for adjustment, particularly of rear brakes of disc/drum brake systems, or need for replacement shoes if adjustment is already at a maximum. Alternatively, it can be due to excessive run-out of the disc. If adjustment or currect run-out does not lessen travel the hydraulic system should be thoroughly checked for leakage. What can cause a "spongy” feel to the pedal? (a) Brakes not properly bled. (b) Cracked or oval brake drum.

(c) New linings not bedded in. (d) Faults within the hydraulic master cylinder. Is it possible to check the operation of the servo unit? This can only be satisfactorily done by the use of vacuum and hydraulic line pressure gauges but an idea may be obtained by exhausting all vacuum by pumping the brake pedal and, with the engine still switched off, allowing the car to roll gently downhill maintaining a steady pressure on the brake pedal. On restarting the engine, the increased braking due to operation of the servo should be noticeable. What are the major causes of inefficient brakes? (a) Grease or oil contaminated linings. (b) Spurious or incorrect grade of lining materials. (c) Glazing, particularly of pads and discs. What causes brake bind and drag? (a) Shoes over-adjusted. (b) Handbrake cable incorrectly adjusted or seized. (c) Sticking pistons in caliper assemblies due possibly to failure to clean them when fitting replacement pads. (d) Pressure build-up due to swollen seals as a result of use of wrong type of brake fluid. In the event of failure of the vacuum supply to the servo unit do the brakes still work?

Yes, the servo is so

designed that if the vacuum supply fails the braking system becomes a straightforward hydraulic system but increased pedal efforts will be required.

What causes the fluid level to drop without anv visible leakage?

Normal disc brake pad wear will cause a gradual fall in fluid level but any excessive sudden fall mav be attributable to internal leakage within the servo unit if fitted.

What are the major reasons for brake pull? (a) Mixed tyres or incorrect tyre pressures. (b) Inefficient dampers. (c) Damaged or worn suspension affecting steering geometry. (d) Contaminated or worn-out lining materials.

What can cause brake judder or flutter of the brake pedal?

(a) Damaged or worn suspension.

(b) Distorted brake disc or drum.

(c) Contaminated lining materials. Can brake drums and discs be reground or skimmed?

This is possible within certain limits but because of the special machinery required to attain the surface finish and tolerances, it is sometimes found to be uneconomic compared to the cost of a factory replacement component.